Correlating Transport with Ionomer Membrane Structure from Molecular to Micron Scales

非技术：离子聚合物膜用于净化水，将化学能转化为电能（电池和燃料电池），并进行各种化学分离。 通过控制膜的化学结构，可以产生所需的高导电性（但柔软且液体状）区域，该区域被机械和化学上坚固的区域包围和支撑。 设计新膜的关键问题在于了解膜中这些不同区域的细节，以及这些区域如何影响水和离子（如锂，钠和氯化物）的运动（运输）。 该项目汇集了不同的技术和理论，包括核磁共振（NMR），计算模拟，电子显微镜和X射线分析，以了解膜结构如何影响性能。 事实上，膜行为的新见解只能从这样一个综合的多学科方法中产生。 这些新的基础知识将使膜结构的设计能够加速离子和水的运动。 反过来，这些设计上的进步将为工程师和企业家提供有价值的信息，以提高水净化系统和先进电源等设备的效率并降低其成本。 由于膜技术代表了一个150亿美元（且不断增长）的商业市场，这些进步可能会给美国的生产力和竞争力带来巨大的收益。 该项目还涉及本科生和研究生的教育和培训，以及K-12教育推广。技术：反渗透水淡化和燃料电池等膜分离应用涉及水、醇和离子的选择性传输通过含离子聚合物（离聚物）。是什么影响了这些不同的移动的物质在离聚物膜内的运输？ 这些效应可以被认为是由两个主要贡献的组合引起的：1）局部分子间相互作用，例如离子和水缔合、聚合物链拓扑结构或酸性; 2）形态特征，例如相对称性（圆柱形、层状、立方形）和域尺寸和性质。该项目将致力于建立一个实验和理论框架，以定量分离和从根本上理解影响运输的这两个主要制度。 通过将一系列尖端的核磁共振（NMR）方法与分子动力学模拟、显微镜和X射线分析相结合，该项目将系统地研究水和离子扩散以及离聚物膜内部的局部分子间缔合，从而对这些材料的渗透性和选择性建立更全面的机理理解。从现有的分子输运理论、流体渗透理论、电解质输运理论和定向软物质理论出发，对膜行为进行新的思考和理论。 在更广泛的背景下，该项目的目标是设计所有新材料，这些材料更便宜，能源使用更有效，更坚固，更适合所需的任务。 参与该项目的学生和合作者将获得聚合物膜行为的复杂和基础知识。 这些新知识将被整合到弗吉尼亚理工大学校园的本科生和研究生聚合物科学课程中，并在弗吉尼亚州西南部新河谷地区的K-12教育推广计划中向儿童及其父母传播。

NON-TECHNICAL:Ionic polymer membranes are used to purify water, convert chemical energy to electrical energy (batteries and fuel cells), and conduct a wide variety of chemical separations. By controlling membrane chemical structure, it is possible to generate desirable highly conductive (but soft and liquid-like) regions that are surrounded and supported by mechanically and chemically robust regions. A key problem in designing new membranes lies in understanding the details of these various regions in the membranes, and how these regions affect the movement (transport) of water and ions such as lithium, sodium, and chloride. This project pulls together disparate techniques and theories, including nuclear magnetic resonance (NMR), computational simulations, electron microscopy, and X-ray analysis, to understand how membrane structure influences properties. Indeed, new insights into membrane behaviors can only arise from such a combined multi-disciplinary approach. Such new fundamental knowledge would enable the design of membrane structures to accelerate ion and water motions. In turn, these advances in design would provide valuable information to engineers and entrepreneurs to increase the efficiency and decrease the cost of devices such as water purification systems and advanced power sources. Since membrane technology represents a $15B (and growing) commercial market, such advances could bring huge gains in US productivity and competitiveness. The project also involves education and training of undergraduate and graduate students, as well as K-12 educational outreach.TECHNICAL:Membrane-separations applications such as reverse-osmosis water desalinization and fuel cells involve the selective transport of water, alcohols, and ions through an ion-containing polymer (an ionomer). What effects drive the transport of these various mobile species inside an ionomer membrane? These effects can be thought to arise from a combination of two major contributions: 1) local intermolecular interactions such as ion and water associations, polymer chain topology, or acidity; 2) morphological features such as phase symmetry (cylindrical, lamellar, cubic) and domain sizes and properties. This project will work toward an experimental and theoretical framework for quantitatively separating and fundamentally understanding these two major regimes that affect transport. By combining an array of cutting-edge nuclear magnetic resonance (NMR) methods combined with molecular dynamics simulations, microscopy and X-ray analyses, this project will systematically study water and ion diffusion as well as local intermolecular associations inside ionomer membranes and thus build a more comprehensive mechanistic understanding of permeation and selectivity in these materials. Starting with existing theories of molecular transport, fluid permeation through porous media, electrolytic transport, and oriented soft matter, new thinking and theories will arise regarding membrane behaviors. In a broader context, this project aims toward design of all new materials that are less expensive, more efficient in energy use, more robust, and more specific to desired tasks. Students and collaborators involved in this project will gain sophisticated and fundamental knowledge of polymer membrane behaviors. This new knowledge will be integrated into undergraduate and graduate polymer science classes on the Virginia Tech campus, and propagated to children and their parents in a K-12 educational outreach program in the New River Valley region of Southwest Virginia.